Disposable strap-type handcuffs are coming into widespread use by law enforcement agencies. These devices are made up of an elongated strap of a strong plastic such as nylon, with a head mounted on one end. The head is provided with a single high-strength steel barb for engagement with the strap near its other end when threaded through the head. A central groove runs the entire length of the strap, permitting it to be locked in an infinite number of positions. This provides a one-way locking action. The strap may be tightened by pulling, but once in place, it may not be loosened. As a result, the strap is not removable for reuse, but rather is removed by cutting and is then discarded. Such a device is available from Becton Dickenson under the designation FLEX-CUF.RTM.. Strap-type handcuffs provide important advantages in that they are lightweight and are easily carried in large numbers, thus expediting the application of restraints in mass arrest situations. They also are inexpensive, have high strength, and are readily adaptable to various methods of application for binding hands together with feet or immovable objects.
A problem associated with the use of strap handcuffs of the type described above is that only a slight margin exists between having the straps engaged so loosely that the prisoner's hands can be worked free or so tightly that circulation is cut off. The strap is relatively narrow and may be readily pulled tight enough to cut off blood circulation, particularly on the palm side of the wrist. Thus a high degree of caution has been required in applying such handcuffs.
Various prior patents disclose strap-type handcuffs and conventional metal handcuffs with shields or plates disposed between closeable bracelets. These patents include U.S. Pat. Nos. 4,071,023; 3,740,977; 3,616,665; and 375,945. None of these patents, however, discloses use of a keeper plate to enable fastening strap handcuffs securely with less danger of cutting off a prisoner's circulation.